In recent years, disk recording density of a disk unit has been increased at a rate of 10% per year. A head for recording and reproducing data on a disk is generally mounted on a slider. The slider with a head mounted thereon is fixed to a side opposing the disk at one end of an actuator arm. At another end of the actuator arm is disposed a voice coil motor (hereinafter called VCM). The actuator arm is rotated by the VCM, thereby positioning the head to a predetermined track position of the disk for performing a recording or reproducing operation.
For recording data on a disk at higher densities, it is necessary to position the head against the disk with greater accuracy. However, with a configuration in which the actuator arm is rotated by the VCM for positioning the head, it is very difficult to further improve head positioning accuracy. On the other hand, in Japanese Laid-open Patent 2002-134807, besides a system for rotating an actuator arm by a conventional VCM, a two-step actuator system using a piezoelectric actuator with paired thin film piezoelectric elements, fixed on a flexure with a head, is proposed for highly accurate positioning of the head to a predetermined track position.
A method of manufacturing the paired thin film piezoelectric elements will briefly be described in the following. First, a surface electrode layer of platinum (Pt) or the like is formed on a substrate such as magnesium oxide monocrystalline substrate (MgO substrate), followed by forming a lead zirconate titanate (PZT) layer, and further, on the PZT layer is formed an upper electrode layer of Pt or gold (Au). Two substrates provided with these layers are prepared, and the upper electrodes are bonded to each other by using an adhesive agent. Subsequently, one of the substrates is removed by etching, and the remaining structure is processed into a desired shape by photolithography and an etching process. Finally, the other substrate is removed by etching and resulting is a single structure of a thin film piezoelectric element, which is secured by bonding to the flexure.
FIG. 10 and FIG. 11A to FIG. 11C depict steps in which, after performing main portions of this manufacturing method, a plurality of thin film piezoelectric elements are formed on a substrate, and the substrate is removed by etching to separate the thin film piezoelectric elements from the substrate. As shown in FIG. 10, a plurality of thin film piezoelectric elements 80 are formed on substrate 91, such as an MgO substrate. FIG. 10 is a plan view as viewed from above the substrate 91. Also, FIG. 11A to FIG. 11C are sectional views.
To separate these thin film piezoelectric elements 80 from the substrate 91, the thin film piezoelectric elements 80 are bonded by adhesive layer 92 onto a temporary fixing substrate 93 together with the substrate 91. This is shown in FIG. 11A. Next, in a state that the temporary fixing substrate 93 and the substrate 91 are bonded to each other by the adhesive layer 92, the substrate 91 is removed by etching. This is shown in FIG. 11B. In so doing, it is required to select an etching solution for etching the substrate 91, which does not cause the temporary fixing substrate 93 and the adhesive layer 92 to be etched. Thereafter the entire structure of the temporary fixing substrate 93, along with the thin film piezoelectric elements 80 bonded thereto is immersed into a chemical solution tank (not shown) to dissolve the adhesive layer 92 in the chemical solution tank. Then the thin film piezoelectric elements 80, in a state of being separated from the substrate 91 and the temporary fixing substrate 93, are obtained. This is shown in FIG. 11C. It is necessary to select a chemical solution for etching the adhesive layer 92, which does not cause the thin film piezoelectric elements 80 to be etched.
However, in such a conventional manufacturing method, with the adhesive layer 92 dissolved in the chemical solution tank, the thin film piezoelectric elements 80 will be separated into individual pieces in the chemical solution tank. Consequently, the thin film piezoelectric elements come into contact with each other and may be sometimes damaged. Further, although it is not shown, during a cleaning process executed subsequently, the thin film piezoelectric elements similarly come into contact with each other and may be sometimes damaged. Also, after the thin film piezoelectric elements 80 are inspected on the substrate 91, if they are separated into individual pieces in the chemical solution tank, it will make discrimination from this inspection difficult. Therefore, there arises a problem in that the separated piezoelectric elements must be individually inspected. Further, it is difficult to automate an operation to remove the thin film piezoelectric elements 80, as loose pieces, from the chemical solution tank or a cleaning tank.